The present invention relates to a web printing press, and more particularly to a web printing press which is adapted for continuously printing a series of different jobs or runs. In the printing of short runs, it is desirable to effect a change from one run to the next quickly without "down time" and with a minimum loss of web material.
With respect to printing presses generally, the prior art has provided apparatus such as that shown in U.S. Pat. No. 3,139,025 to Chambon. The Chambon patent discloses direct printing apparatus in which runs of different printed context may be made by a series of rotary printers located along the path of a web and adapted to be alternately operated. While a first printing set is printing on the web, the second printing set may be made ready for the next run and after reaching a predetermined count, the first printing set is thrown off and the second printing set engaged with no loss of paper occasioned by the shift from the first printing set to the second printing set. Also as is well known, printing presses have been automated and control systems have been associated with presses to control the various printing units as desired by the press operator. Typical of patents which disclose such is U.S. Pat. No. 3,467,007.
The present invention relates to a web printing press which includes multiple printing units, a web infeed, a folder and other apparatus, such as chill rolls, etc. Specifically, the web printing press is a blanket to blanket offset lithographic press designed for printing short runs. In accordance with the present invention, a web may be moved through a unit or units which are in a printing mode, i.e. thrown-on, and a unit or units which are not in a printing mode, i.e. thrown-off. The units which are thrown-off may be made ready for the next job, while the other unit or unis are printing a different job.
A control system functions to control throw-on of the dampeners and inker of each unit as well as the blanket cylinder of each unit at the appropriate time so that a minimum of web material is wasted, i.e. where one job stops the next job starts. The control system is such that an operator may control the units so that any one or all of the units may print one job.
More specifically, the web press of the present invention utilizes individual motors associated with each printing unit. These motors are large enough to power the entire web press including both the printing units and the auxiliary units. A common drive line extends through the press and a single position clutch is associated with each unit and coacts between the common drive line and the motor for its unit. Upon engagement of a clutch, the motor of that printing unit is drivingly connected to the common drive line. Upon disengagement of a clutch the unit may be driven independently of the other units on the press for "make ready" purposes, and for bringing the printing unit up to a predetermined speed and into a predetermined condition prior to throw-on of the unit.
The present invention provides, therefore, a web press system which is especially suited to short runs of different printed matter and characterized by rapid changeover from one run to the next run with minimum loss of time and paper. While one printing unit is printing on the web, a second printing unit may be made-ready while the web continues to move through both of the units.
The present invention also provides a novel press driving arrangement including a main drive shaft and clutch means coacting between the shaft and a free running shaft ring gear which is driven from a power shaft connected to the individual printing unit motors.
Further, the present invention is embodied in a web offset lithographic press wherein each printing unit includes a cylinder system for offset printing including a pair of plate cylinders and a pair of blanket cylinders which desirably engage the web in an S-wrap configuration and print on both sides of the web simultaneously. Means are provided for selectively throwing-off each printing unit and for changing the path of the web as it passes between the thrown-off blanket rolls. This is done so that the web is restrained from flutter and contact with the thrown-off blanket cylinders as it passes the nonprinting unit. Lever arm supported grator rolls coacting above and below the web adjacent to and on opposite sides of the nip of the blanket cylinders are provided to change the attitude of the web as it traverses the nip. The grator rolls are driven up to the speed of the web prior to engaging the web.